Side gas seal means for rotary mechanisms

ABSTRACT

The improved side gas seal comprises a seal strip disposed in a groove in the rotor face adjacent each of the flank portions of the rotor. The seal strip is resiliently biased in a direction outwardly of the groove by a spring means. The radially outer surface of the seal strip is provided with at least one recess for communicating the interstices between the rotor face and housing wall with the space between the bottom of the groove and the anti-seal side of the seal strip to thereby pass pressurized gas to the space behind the seal strip. This pressurized gas provides a force supplementing the force of the spring means acting against the seal strip and assists in urging the seal strip outwardly of the groove and into sealing abutment against the adjacent housing wall surface.

United States Patent [1 1 I Siler [4511 Sept. 10, 1974 SIDE GAS SEALMEANS FOR ROTARY MECHANISMS Primary Examiner-John J. Vrablik [75]Inventor: Charles A. Siler, Menomonee Falls, Attorney Agent orFirm-Arthur Frederick Wis. [73] Assignee: Outboard Marine Corporation,[57] ABSTRACT Waukegan, Ill. The improved side gas seal comprises a sealstrip disposed in a groove in the rotor face adjacent each of [22]Flled' May 1973 the flank portions of the rotor. The seal strip isresil- [21] Appl. No.: 356,462 iently biased in a direction outwardly ofthe groove by a spring means. The radially outer surface of the seal[52] U S C 418/142 277/76 strip is provided with at least one recess forcommuni- [5 I] 5/00 F04: 27/00 cating the interstices between the rotorface and hous- [58] Fie'ld 4187142 277/76 ing wall with the spacebetween the bottom of the groove and the anti-seal side of the sealstrip to [56] References Cited thereby pass pressurized gas to the spacebehind the seal strip. This pressurized gas provides a force supple-UNITED STATES PATENTS menting the force of the spring means actingagainst 3,109,661 11/1963 Swain et a]. 277/76 the seal strip and assistsin urging the seal strip out- Hamada ardly of the groove and intosealing abutment against FOREIGN PATENTS OR APPLICATIONS the dja nt husing wall surface.

967,040 8/1964 Great Britain 418/l42 l,55 1,099 2/1970 Germany 418/142 5Chums 4 Drawmg' figures PAIENIEB SEP '1 01914 A FIG.

Q Mir... 1 BE.

SIDE GAS SEAL MEANS FOR ROTARY MECHANISMS DISCLOSURE This inventionrelates to rotary mechanisms and, more particularly, to seal means forsealing the interstices between the rotor faces and the adjacent housingwall surfaces.

BACKGROUND OF THE INVENTION In rotary mechanisms, such as rotaryinternal combustion engines of the Wankel type as disclosed in the U.S.Pat. No. 2,988,065 to Wankel et al., it is customary to provide in eachof the end faces of the rotor an annular oil seal and gas seals disposedoutwardly of the oil seals. The gas seals of the segmental type disposedadjacent each of the flank portions of the rotor usually coact at theiropposite ends with an apex seal assembly which includes an apex pin toeffect thereby a substantially complete fluid seal between each of therotor faces and the associated housing surfaces. Each of the segmentalgas seals is located in an arcuate groove and is resiliently biased in adirection outwardly of the groove by a spring means. Many side sealdesigns have been developed to increase the sealing effectiveness, someof such development effort is exemplified in the following United StatesPatents:

Wankel et a1 U.S. Pat. No. 2,880,045 Bentele U.S. Pat. No. 2,979,042Wankel U.S. Pat. No. 3,064,880 Bentele U.S. Pat. No. 3,033,180 HurleyU.S. Pat. No. 3,081,745 Schlor U.S. Pat. No. 3,102,520 Scherenberg et alU.S. Pat. No. 3,131,945 Simonsen U.S. Pat. No. 3,139,233 Froede U.S.Pat. No. 3,142,439 Bentele U.S. Pat. No. 3,176,910 Paschke U.S. Pat. No.3,251,541.

In some of these patents the side seals are shown spring biased towardthe housing end wall while as shown in the Paschke patent, side sealsare biased by gas pressure.

Accordingly, an object of this invention is to provide an improved gasseal means for a rotary mechanism which reduces gas leakage rates fromthe working chambers and provides a rotary mechanism with improved poweroutput and fuel economy.

Summary Accordingly, the present invention contemplates an improved gassealing means for a rotary mechanism of the Wankel type, which gassealing means comprises an elongated seal strip disposed within a groovein the face of the rotor and extending adjacent each flank portion ofthe rotor. A resilient biasing means, as for example a wavy metallicstrip or ribbon, is disposed between the seal strip and the bottom ofthe groove to urge the seal strip in a direction outwardly of the grooveand into engagement with the adjacent housing wall. The seal strip isprovided with at least one notch in the radially outer surface of thestrip so as to define with the radially outer surface of the groove apassageway. The passageway functions to communicate the space betweenthe rotor face and the adjacent housing wall with the space between theseal strip and bottom of the groove so that the strip surface oppositefrom its sealing surface (hereinafter referred to as the anti-sealingsurface") is subjected to gas pressure. This relatively high gaspressure assists the resilient biasing means in urging the seal stripinto abutment against the adjacent housing wall.

Another feature of the present invention is the provision of a chamferalong the radial outer edge of the sealing surface of the seal strip.This chamfer is dimensioned in relation to the depth of the notch sothat seal strip maintains uninterrupted sealing engagement with thehousing wall as the seal strip tilts or rocks within the groove undervarying gas pressures to which the seal strip is subjected. Bymaintenance of continuous seal ing contact of the seal strip with thehousing wall, gas from the interstice between the housing wall and rotorface radially outwardly of the seal strip is prevented from bypassingthe seal strip through the notch.

In a more limited aspect the present invention provides a plurality ofarcuate-shaped notches so that gas communicates with the anti-sealingsurface of the seal strip via a plurality of passageways.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fullyunderstood from the following detailed description thereof whenconsidered in connection with the accompanying drawing wherein but oneembodiment of the invention is illustrated by way of example, and inwhich:

FIG. 1 is a diagrammatic transverse view of a rotary mechanism havingside gas seals according to this invention;

FIG. 2 is an enlarged fragmentary view showing in elevation a portion ofthe side gas seals of this invention shown in FIG. 1;

FIG. 3 is a cross-sectional view taken substantially along line 3-3 ofFIG. 2, shown somewhat on an enlarged scale; and

FIG. 4 is a view similar to FIG. 3 showing the side gas seal in a tiltedposition,

Description of the Preferred Embodiment Now referring to the drawingsand, more specifically to FIG. 1, the reference number 10 generallyrefers to a side gas seal according to this invention for a rotarymechanism of the Wankel type, such as an internal combustion engine ofthe kind disclosed in the U.S. Pat. No. 2,988,065.

As illustrated, rotary mechanism 10 comprises a rotor 12 which issupported for eccentric rotation within a cavity formed by a housing 14.The housing 14 of a single rotor mechanism comprises two end walls 18held in spaced relationship to each other by an intermediate wall 20which defines an epitrochoidal peripheral inner surface 22. The rotor 12has one more apex portion than the number of lobes formed by the housingcavity so that in the rotary mechanism 10 herein illustrated, the rotorhas two opposite generally triangular shaped faces 23 each of which hasthree apex portions 24, while the cavity has two lobes. The rotor hasthree peripheral surfaces or flanks 26 which define with the housingcavity three working chambers A, B, and C which successively expand andcontract in volumetric size as rotor 12 rotates within housing 14.

As shown, if rotary mechanism is an internal combustion engine, an inletport 28 may be provided to admit a mixture of fuel and air into chamberA. An exhaust port 30 may be provided to communicate with chamber B topass spent products of combustion from the engine. An ignition means 32,such as a spark plug, may be provided to ignite the compressed fuel andair mixture in chamber C so that the expanding products of combustionrotatively drive rotor 12 in a counterclockwise direction.

The mechanism is provided with sealing means to seal the intersticesbetween rotor 12, epitrochoidal surface 22, and the inner surface 16 ofend walls 18 to minimize intercommunication between chambers A, B and C.As is conventional, each apex portion 24 of rotor 12 is provided with anapex seal 34 which projects radially from rotor 12 to engage theepitrochoidal surface 22. The space 36 between each rotor face 23 andthe adjacent surface 16 of end walls 18, which space 36 communicateswith chambers A, B, and C, is sealed by gas seal means according to thisinvention. To prevent leakage of oil into the chambers A, B, and C, froman area adjacent the crankshaft 38, an oil seal 40 is carried in each ofthe faces 23 of the rotor.

The gas seal means according to this invention comprises a plurality ofarcuate-shaped seal strips 42, each of which is disposed for slidablemovement in a groove 44 formed in each face 23 and adjacent each flank26 of the rotor. A resilient biasing means of any suitable type, such asa wavy spring steel strip or ribbon 46, is disposed between the bottomof groove 44 and the antiseal side 48 of seal strip 42 to urge the sealstrip 42 into abutment against surface 16 of end wall 18 (see FIG. 3). Aplurality of spaced, arcuate-shaped notches or recesses 50 are providedin the radially outer surface 52 of the seal strip so as to communicatespace 36 between rotor face 23 and surface 16 of the adjacent end walls18 with the space between the bottom of groove 44 and anti-seal side 48of seal strip 42. With the space behind seal strip 42 in unrestrictedcommunication with space 36 and, hence the gas pressures in workingchambers A, B and C, the anti-seal side 48 of seal strip 42 is subjectedto those gas pressures. Since the area on the sealing side of seal strip42 exposed to the gas pressures in space 36 is less than the area ofanti-seal side 48 of seal strip 42, the net force exerted by the gaspressure is in a direction urging seal strip 42 toward surface 16. Thisgas exerted force supplements the force of spring 46 to maintain sealstrip 42 in sealing engagement with surface 16.

As best illustrated in FIG. 4, each of the seal strips 42 is subjectedto tilting or rolling about its crosssection centroidal axis and withinthe limits permitted by the tolerances between the dimensions of groove44 and seal strip 42. To insure that under this movement of seal strip42 an uninterrupted seal between the seal strip and surface 16 ismaintained, the radially outer edge of seal strip 42 is provided with achamfer 54. This chamfer 54 extends in the sealing surface of the sealstrip, from a point at or below the deepest part of recesses 50 insurface 52 of the seal strip, to radial outer surface 52. The chamfer 54presents to surface 16 an uninterrupted contact line 56 (see FIG. 2) inthe tilted position of the seal strip so that gas in space 36 cannotbypass the seal strip through the recesses 50 which bypassing wouldoccur in absence of chamfer 54 and the line contact 56.

In tests comparing gas seal strips 42 having seven recesses 50 withconventional gas seal strips (only spring biased), substantialreductions in gas leakage rates have been achieved by gas seal strips 42according to this invention. More specifically, at 3,000 rpm of the testengine, the gas leakage rate was 31 percent less than the leakage rateof the conventional seal strips, at

4,000 rpm the gas leakage rate was 42 percent of the leakage rate of theconventional seal strips, and at 5,500 rpm the gas leakage rate wasreduced by 54 percent. Under wide open throttle conditions of engineoperation, the gas leakage rate was 54 percent less than the leakagerate when conventional seal strips were employed in the engine.

It is believed now readily apparent that the present invention providesan improved gas seal strip for a rotary mechanism which substantiallyreduces gas leak age through the interstice between the rotor face andhousing end walls. It is a gas seal which has the effect of improvingthe power output of the mechanism.

Although but one embodiment of the invention has been illustrated anddescribed in detail, it is to be expressly understood that the inventionis not limited thereto. Various changes can be made in the arrangementof parts without departing from the spirit and scope of the invention asthe same will now be understood by those skilled in the art.

What is claimed is:

1. An improved side gas seal assembly for a rotary mechanism having arotor comprising opposite face portions and a plurality of peripheralflank portions, the rotor being supported for eccentric rotation in acavity formed in a housing defining a peripheral trochoidal surface andwall surfaces adjacent each of said rotor face portions, the side gasseal assembly comprismg:

a. a groove in each rotor face extending adjacent each flank portion ofsaid rotor;

b. a seal strip for each groove having a sealing side,

an anti-sealing side, and radial inner and outer surface portions;

c. each of said seal strips being disposed in each of said grooves withthe sealing side projecting from said groove and the anti-sealingsurface adjacent the bottom portion of said groove;

d. resilient biasing means for each seal strip disposed in said grooveto urge the associated seal strip in a direction outwardly from itsassociated groove and the sealing side into abutment against theadjacent wall surface;

. recess means in each of said seal strips to communicate the spacebetween the rotor face and the adjacent housing wall surface and thespace between the anti-sealing surface of the seal strip and the bottomof the associated groove to conduct pressurized gas to the latter spaceand thereby exert a force on said seal strip directed outwardly of itsassociated groove; and

f. the sealing side of the seal strip is provided with a chamferedportion which extends from at least the depth of the recess means toprovide an uninterrupted sealing line engaging the adjacent wall surfaceand extending the full length of the seal strip when the seal striptilts relative to its associated groove to thereby prevent pressurizedgas from bypassing the seal strip.

2. The apparatus of claim 1 wherein said seal strip is substantiallyrectangular in cross-section.

3. The apparatus of claim 1 wherein said recess means is located in theradial outer surface portion of said seal strip to define with thegroove a passageway means.

4. The apparatus of claim 1 wherein said recess means is a plurality ofspaced notches in the radial outer surface portion of the seal strip todefine with the groove a plurality of passageways.

5. The apparatus of claim 4 wherein each of said notches is arcuate inshape and extend from the sealing side to the anti-sealing side of theseal strip.

1. An improved side gas seal assembly for a rotary mechanism having arotor comprising opposite face portions and a plurality of peripheralflank portions, the rotor being supported for eccentric rotation in acavity formed in a housing defining a peripheral trochoidal surface andwall surfaces adjacent each of said rotor face portions, the side gasseal assembly comprising: a. a groove in each rotor face extendingadjacent each flank portion of said rotor; b. a seal strip for eachgroove having a sealing side, an antisealing side, and radial inner andouter surface portions; c. each of said seal strips being disposed ineach of said grooves with the sealing side projecting from said grooveand the anti-sealing surface adjacent the bottom portion of said groove;d. resilient biasing means for each seal strip disposed in said grooveto urge the associated seal strip in a direction outwardly from itsassociated groove and the sealing side into abutment against theadjacent wall surface; e. recess means in each of said seal strips tocommunicate the space between the rotor face and the adjacent housingwall surface and the space between the anti-sealing surface of the sealstrip and the bottom of the associated groove to conduct pressurized gasto the latter space and thereby exert a force on said seal stripdirected outwardly of its associated groove; and f. the sealing side ofthe seal strip is provided with a chamfered portion which extends fromat least the depth of the recess means to provide an uninterruptedsealing line engaging the adjacent wall surface and extending the fulllength of the seal strip when the seal strip tilts relative to itsassociated groove to thereby prevent pressurized gas from by-passing theseal strip.
 2. The apparatus of claim 1 wherein said seal strip issubstantially rectangular in cross-section.
 3. The apparatus of claim 1wherein said recess means is located in the radial outer surface portionof said seal strip to define with the groove a passageway means.
 4. Theapparatus of claim 1 wherein said recess means is a plurality of spacednotches in the radial outer surface portion of the seal strip to definewith the groove a plurality of passageways.
 5. The apparatus of claim 4wherein each of said notches is arcuate in shape and extend from thesealing side to the anti-sealing side of the seal strip.